Despite an Everest-sized mountain of evidence that Rep. David Rivera orchestrated a sham campaign by an unknown candidate in the Democratic primary, the incumbent has steadfastly denied knowing anything about the case. Rivera also denies being under federal investigation even though multiple sources tell the Miami Herald otherwise.

The move is likely to turn up the heat even more on Rivera, who just got slapped with 11 violations from the Florida Commission on Ethics last week in unrelated cases involving his use of finances as a state rep and a payout from a casino to a company linked to his mom.

Sternad, an unknown hotel employee who ran against Democrat Joe Garcia in the primary, came under scrutiny after spending thousands on ads and mailers without making clear where he got the money.

Since then, the bizarre case has included a disappearing Republican operative tied to Rivera, envelopes of cash and testimony from vendors that the operative, Ana Sol Aliegro, said Rivera was behind the campaign.

In his letter, Sternad writes that he won't report his finances "on the grounds that I may incriminate myself," The Miami Herald reports.

Rivera, who faces a tight reelection fight against Garcia in next week's election, has denied any role in Sternad's campaign.

Tim Elfrink is an award-winning investigative reporter, the managing editor of the Miami New Times and the co-author of "Blood Sport: Alex Rodriguez and the Quest to End Baseball's Steroid Era." Since 2008, he's written in-depth pieces on police corruption, fatal shootings and social justice issues across South Florida. He's won the George Polk Award and has been a finalist for the Goldsmith Prize for Investigative Reporting.